The Changes in Surface Morphology and Mechanical Properties of Poly(3-Hydroxybutyrate) and its Copolymer Films during <i>In Vitro</i> Degradation

Abstract

In the current work, we studied the degradation of PHB films in vitro by pancreatic lipase and in phosphate buffer saline (PBS). We traced the changes in film properties by several analytical methods: the change of weight, surface roughness and morphology (by atomic-force microscopy) and Young’s modulus (by nanoindentation) were measured.PHB is a semicrystalline polymer and thus the films have lamellar structure. During biodegradation, three types of changes were observed on the film surface: appearance of new lamellae, disappearance of lamellae and disintegration of lamellae into shorter fragments. During the six months of polymer films degradation the weight of samples decreased; and an increase in Young's modulus due to the relatively fast degradation of the amorphous areas was observed by nanoindentation.

Adhesion of Escherichia coli and Lactobacillus fermentum to Films and Electrospun Fibrous Scaffolds from Composites of Poly(3-hydroxybutyrate) with Magnetic Nanoparticles in a Low-Frequency Magnetic Field

“…It is important to note that during the fabrication of films through the precipitation of polymers from the solution onto the glass surface, their upper side dries in contact with air, while the lower side dries adjacent to the glass. Related to this is the difference in the roughness of these two sides, which was previously demonstrated by us [ 50 , 51 ] and has been confirmed in the literature [ 52 ]. The roughness of the top side of the film depends on the intensity with which solvent evaporation from its surface took place.…”

“…It is important to note that during the fabrication of films through the precipitation of polymers from the solution onto the glass surface, their upper side dries in contact with air, while the lower side dries adjacent to the glass. Related to this is the difference in the roughness of these two sides, which was previously demonstrated by us [50,51] and has Based on the concept of "sharp edge mediated insertion" of bacterial cells [23,48], it can be assumed that the sharp edges of graphene nanoplatelets extending above the surface of the material can have a bactericidal effect. We investigated the nanotopography of the surface of polymer films by atomic force microscopy (AFM) (Figure 4a-c).…”

Biodegradation of Poly(3-Hydroxybutyrate) and Poly(3-Hydroxybutyrate-Co-3-Hydroxy-4-Methylvalerate) Films by Porcine Pancreatic Lipase

“…The loss of polymer weight due to degradation was determined gravimetrically using a AL-64 balance (Acculab, USA). Every three days the solutions were replaced by the fresh ones [31][32][33][34][35][36]. To avoid bacterial contribution to the degradation of polymers, sodium azide (NaN 3 ) at a concentration of 2 g/l was added to the buffer solution, and the buffer solution was changed twice a week [37].…”

“…Nanoindentation of PHAs Films. Study of the mechanical properties was carried out by method of instrumented nanoindentation according to the requirements of ISO 14577 using scanning nanohardness tester NanoScan-4D (FSBI TISNCM, Troitsk, Moscow, Russia) [34][35][36]. Nanoindentation was performed on the smooth side of the film.…”

“…Molecular weights (Mw) of PHB and PHB-4MV were determined by viscosimetry. The viscosity of the PHB solution in chloroform was measured at 30 °C on a RT RheoTec viscometer (RheoTec Messtechnik GmbH, Germany); the molecular weight was calculated using the Mark-Kuhn-Houwink equation [34][35][36] [η] = 7.…”